Alloy



Patented 29, 1942 UNITED STATES PATENT OFFICE ALLOY Vsevolod Nicholas Krivobok, Pittsburgh, Pa., as-

signor to Rustless Iron and Steel Corporation, Baltimore, Md., a corporation of Delaware Original application January 20,

1934, Serial No. 707,613. Divided and this application July 17, 1937, Serial No.

gnewed October 2, 1939 bright corrosion-resistant metal capable of cold rolling, into sheet, strip and bar stock, which readily lends itself to a variety of working and forming operations, such as drilling, machining, punching, blanking, deep-drawing. pinning and welding to achieve agreat number of products or manufactures, such as tubing and piping, fluid valves, flanges and bolts, pans, vats and tanks, all for high temperature duty, as in stills, evaporator units and the like, for semi-chemical uses in the canning, dairy, oil and photographic film industries, or as in chemical calciners used in the production of paints and dyes, or for valves, valve seats, exhaust manifolds, stacks and the like, as in internal combustion engines, especially automobile and airplane. engines, or for buckets, nozzles and like parts for gas turbines, or like articles, products or manufactures for like high temperature applications.

The invention accordingly consists in the combination of elements, composition of ingredients and mixture of materials, and in the articles, products and manufactures thereof, as described herein, the scope of the application of which is withstanding the corrosive action of various fruit and vegetable acids, is desired. Similarly,

these irons and steels are widely adapted for various chemical plant apparatus and equipment where metal resistant to the corrosive attack of acids, alkalies and salts at room temperature or slightly elevated temperatures, is required.

These austenitic chromium-nickel irons and steels, however, are not satisfactorily adaptable to extremely high temperature duty, especially high temperature duty under strongly oxidizing or corrosive conditions.

One of the objects of my invention is the production of strong, tough and ductile austenitic irons and steels of especially high heat-resistant 5% molybdenum, .5% to 5% cobalt, .03% to .4%

carbon, and the balance substantially iron, with the usual percentages of silicon, sulphur and phosphorus, is produced in a suitable manner, as for example, as described in Patent No. 1,925,182 of Alexander L. Feild, entitled Process for the manufacture of rustless iron.

In the production of my alloy iron and steel the metal is first produced as ingots which are fashioned into blooms or billets in accordance with lmown methods and conveniently hot rolled 15% nickel, and the balance substantially iron) are used in the production of a wide variety of corrosion-resistant and mildly heat-resistant products or articles of manufacture. Thus, these austenitic irons and steels, especially the 18-8 irons and steels (irons and steels containing 18% chromium, 8% nickel, and the balance substantially iron) may bev used in a number of interior or exterior architectural applications, such as decorative trim, ornamentation and fixtures.

Likewise, these irons and steels may be employed into sheet bar and strip bar sizes. These bars are then annealed and pickled and, for example, cold rolled into sheet or strip of desired thick- -ness. My alloy iron and steel is corrosion-resistant and heat-resistant, withstanding the exacting conditions of high temperature duty over long periods of continuous use without grain growth, fatigue or failure. For example, a bar of this austenitic chromium-nickel iron analyzing approximately 18% chromium, 8% nickel, 3% molybdenum, 2% cobalt, .10% carbon, and the balance substantially .iron, subjected to a stress of 8,000 pounds per square inch at a temperature of 1500 F. under oxidizing atmospheric .conditions has a life of about 350 hours. Ordinary 18-8 chromium-nickel iron analyzing approximately, 18% chromium, 8% nickel, .07 carbon, and the balance substantially iron has a life of only about 12 hours to 14 hours under like conditions of operation. 1

My austenitic chromium-nickel iron or steel, in addition to having a life under high temperature operating conditions greatly in excess of that of heretofore known and/or used austenitic chromium-nickel irons or steels, is strong, tough and ductile and readily lends itself to a variety of forming and working operations either from sheet, strip or bar stock. The metal may be forged, upset or pierced, it may be hot or cold rolled into sheet, strip and bar stock, which may be further worked or formed, as by drilling, machining, punching, blanking, deep-drawing, spinning and like operations followed by welding where desired, either with the oxy-acetylene torch or with the electric arc (employing welding rods of approximately the same analysis as the stock welded) to achieve a great, many articles, products and manufactures, such as tubing, fluid valves, couplings, flanges and bolts, tanks, trays and pans, all for high temperature duty, as in boilers, condensers, oil cracking stills, evaporator units and the like, or for semi-chemical uses in the canning, dairy, oil and photographic film industries, or for chemical calciners as used in the production of iron-free chemicals, such as paints and dyes under a variety of corrosion-fostering conditions, including in addition to the gases normally present in the atmosphere, the sulphurbearing gases and vapors encountered in oil stills proximately, 18% chromium, 8% nickel, 1% to 5% molybdenum, .5% to 5% cobalt, .03% to .4% carbon, and the balance substantially iron, is specifically described, good results are achieved where the chromium content ranges between 10% and and the nickel content between 7% and 15%; the higher carbon steels being preferably employed in a variety of cast articles or manufactures, such as furnace parts, ore treating and handling apparatus, high temperature conveyer parts and equipment, and like parts and equipment subjected to corrosive and abrasive conditions in operation at high temperatures.

Certain practical advantages in achieving long-- life austenitic iron and steel at unusually high operating temperatures are achieved by adding the further supplemental ingredients, silicon and aluminum, in amounts up to about 3%; these supplementing amounts of silicon and aluminum are employed either separately or in combination as desired. These ingredients do not materially detract from the physical properties of the metal and directly contribute to the resistance to scaland oil handling equipment, the mineral waters met with in boiler and condenser applications and like corrosive, embrittling and fatiguing conditions. (The various welded parts, articles'or manufactures are preferably heat treated in accordance with well known methods to establish a fully austenitic condition of the metal after the welding is completed in order to prevent intergranular corrosion and assure maximum chem-' ical resistance in actual use.)

In addition, my austenitic chromium-nickel alloy metal stock may be worked or formed, as above indicated, achieving a further variety of high temperature duty articles, parts and accesseries, such as internal combustion engine valves, valve seats, exhaust manifolds, stacks, especially applicable to automotive and aviation duty, or.

gas-turbine buckets, nozzles and like parts requiring strength, toughness, shock-resistance, corrosion-resistance and scale-resistance under high temperature operating conditions.

Thus,'it will be seen that there has been provided in this invention a chromium-nickel alloy and articles, products or manufactures thereof,

in which the various objects hereinbefore noted,

together with many thoroughly practical advantages are successfully achieved. It will be seen that the alloy is strong, tough, corrosion-resistant and heat-resistant and that it readily lends itself to working or forming into a variety of commercial products or manufactures, a number of which are set forth above, which are especially adapted to withstand continuous high temperaing at high temperatures. Where unusually high temperatures are encountered such supplementary additions are highly beneficial.

As many possible embodiments may be made of my invention and as many changesmay be made in the embodiment hereinbefore set forth, it is tobe understood that all matter described herein is to be interpreted as illustrative, and not in a limiting sense.

I claim:

1. In manufactures of the class described, substantially austenitic wrought stainless steel articles for use under conditions of high temperatures where an atmosphere of sulphur-bearing gases and vapors is encountered, the composition of said articles comprising as essential ingredients 10 per cent to 25 per cent chrominum, 7 per cent to '15 per cent nickel, 1 per cent to 5 per cent molybdenum, .5 per cent to 5 per cent cobalt, .50 per cent to 3 per cent of one of the group comprising silicon and aluminum, .03 per cent to .4 per cent carbon, and the balance consisting of iron.

4 2. In manufactures of the class described, substantially austenitic wrought stainless steel arture duty over long periods of time and under the many varying conditions of actual, practical use.

While as illustrative of my invention an austenitic chromium-nickel alloy containing apticles for use under conditions of high temperatures where an atmosphere of sulphur-bearing gases and vapors is encountered, the composition of said articles comprising as essential ingredients 10 per cent to 25 per cent chrominum, 7 per cent to 15 per cent nickel, 1 per cent to 5 per cent molybdenum, .5 per cent to 5 per cent cobalt, .50 per cent to 3 per cent; silicon, .03 per cent to .4 per cent carbon, and the balance consisting of iron.

cent to 3 per cent aluminum,.03 per cent to .04

per cent carbon, and the balance consisting of iron.

VSEVOLOD N. KRIVOBOK.

3. In.manufactures of the class described, sub- 

